Recently, the number of documents made in offices, etc., has become very enormous, and it has strongly been desired to develop a system capable of recording and reproducing these documents at any time.
Hitherto, as a long transparent light-sensitive material (the term "long rolled recording material" used in this invention means a recording material having the length to width ratio of more than 20/1) which is used in a rolled state, there are known cinema film and microfilm using silver halide, and film using a diazo compound. In order that after forming images at optional position(s) of the above-described light-sensitive recording material by applying thereto image exposure and development, images are formed at other portion(s) of the same recording material by repeating the same operation as above, very complicated steps and apparatus are required and it is very difficult for practical use to form images at optional position(s) of the above-described recording material at any time and repeatedly performing retrieving, projecting, and reading of the images thus recorded according to requirement.
As a system capable of forming images at any position(s) of the same recording material at any time, a system of using an electrophotographic recording material, a heat developing type light-sensitive material, or a post active type dry image forming material may be considered in principle. However, a system capable of forming images at optional positions of the same light-sensitive material at any time and retrieving, projecting and reading the recorded images according to requirement has not yet been sufficiently realized.
In such a system of forming images at optional positions of the same recording material at any time and repeatedly performing the operations such as retrieval, projection, reading, duplication, etc., of the images at any desired position of the recording material according to requirement, there are various problems. For example, in the system of using a long rolled recording material, it becomes inevitably necessary to run the recording material, and when a long rolled recording material is run, there are disadvantages such as that scratches, etc. form on the surface of the light-sensitive layer of the recording material due to contact between the recording material and rollers, guide pins, etc. necessary for moving and guiding the recording material, and also physical defects or delicate changes in the surface state, etc., such as transfer of the surface state of the back surface of the recording material onto the surface of the light-sensitive layer which is brought into contact with the back surface or the transfer of the surface state of the light-sensitive layer onto the back surface, the retransfer of materials once transferred onto guide rollers, etc., onto the surface of the light-sensitive layer, blocking on the surface of the light-sensitive layer, etc. occur, and , when images are newly formed after running the recording material, the quality of the new images is greatly reduced as compared with the images formed before running.
Also, when such a long rolled recording material is stored in the rolled state for a long period of time, defects such as the reduction in the quality of images, etc. occur by the direct contact of the light-sensitive layer of the recording material with the back surface thereof (e.g., due to the occurrence of blocking, etc.).
In particular, in the case of a recording material of the type that images are recorded as reduced images thereof, it is required to enlarge and project the images at reading, whereby the above-described defects are also enlarged to cause large problems.
In the case of an electrophotographic recording material, the surface state of the light-sensitive layer thereof is very important in the image forming process, as is well known. That is, in an electrophotographic process, after first uniformly electrostatically charging the surface of a light-sensitive layer, the light-sensitive layer is imagewise exposed to form latent images and the latent images are toner-developed. Accordingly, when even very delicate changes occur in the property or the state of the surface of the light-sensitive layer, they have large influences on the quality of images formed.
It is known to form a surface protective layer containing a hardenable compound or fine particles in an electrophotographic light-sensitive material. Examples of adding a hardenable compound are described in Japanese Patent Application (OPI) Nos. 30526/75, 3538/79, 1632/79, 40839/81, etc., and examples of adding fine particles are described in Japanese Patent Application (OPI) Nos. 26226/77, 38054/81, 229571/84, etc. (the term "OPI" as used herein means an "unexamined published Japanese patent application"). However, these protective layers are all for opaque (non light-transmissive) light-sensitive materials, and the purpose of them is in the capability of the repeated use of the same light-sensitive material (i.e., the improvement of the copying life) by preventing the occurrence of abrasion by the contact of the light-sensitive material onto which the toner images are transferred and the formation of scratches by the contact with toner particles or in a cleaning step.
In the case of ordinary plain paper copying (PPC), toner images formed on a light-sensitive recording material are transferred onto a paper, etc., to form images thereon. Accordingly, fine scratches and dust formed on the surface of the light-sensitive layer and microscopic defects in property or state on the surface of the light-sensitive material are not transferred onto the paper, etc., as enlarged defect images, and do not give serious disadvantages for practical use.
Also, in the case of PPC or CPC (coated paper copying) copying without employing the transfer of toner images, the enlargement and projection of the light-sensitive material itself are generally unnecessary at reading, and hence the above-described fine various defects on the light-sensitive material do not give any serious disadvantages for practical use.
However, in the case of directly utilizing images formed on a transparent (light transmissive) light-sensitive recording material without employing an image transfer process, even the above-described fine defects become large problems. In particular, in the system of recording images on a transparent light-sensitive recording materials as reduced or diminished images, the images are projected as enlarged images at reading and hence if, in such a case, various fine defects exist on the surface of the light-sensitive layer thereof, they become large problems for practical use.
In the case of forming images on a transparent light-sensitive recording material using the above-described electrophotographic process, the surface state of the light-sensitive layer thereof is important. In other words, when images are first formed at optional position(s) of a transparent light-sensitive recording material and then images are formed again at other position(s) of the same recording material after running the recording material from several dozen times to several thousand times of after storing the recording material in a rolled state for a long period of time, defects such as scratches, etc., as well as fine spot-like or image-like uneven densities are observed on the surface of the light-sensitive material. This results in reduction of the readability, and reductions in the resolving power of characters and in the quality of continuous tone images. In particular, in a microfilm system using a transparent electrophotographic recording material, the reduction of the quality of images is severe, and thus such images are unsuitable for practical use. This trouble is considered to be partially caused by scratches occurring during running or during the storage of the recording material in rolled state, attachment of dust on the surface of the light-sensitive layer, the occurrence of blocking, etc. In addition to these defects on the surface, other defects which are considered to be caused by delicate changes in property or state of the surface of the light-sensitive material unobservable by a microscope occur and it is very important for practical use to prevent the occurrence of such defects.
The inventors previously found that, in an image-forming process of performing image formation more than twice on the same light-sensitive material by a sequence of steps including at least image exposure and development, the above-described various defects could be substantially eliminated by forming on the surface of the light-sensitive material a surface protective layer containing a hardenable compound or a surface protective layer containing fine particles. The light-sensitive recording material having such a surface protective layer can be used without any trouble in practical purpose in a system of forming conventional microfilm images for recording originals mainly composed of line images such as characters or letters, etc. However, when a continuous tone image is formed on the light-sensitive material having the above-described surface protective layer after running the recording material or after storing the recording material in a rolled state for a long period of time, very fine uneven densities, etc. occur in what should be uniform density ranges, which results in reducing the quality of images as compared with the images formed on the same recording material before running or storage for a long period of time. For preventing the reduction in the quality of the continuous tone images in the case of forming the surface protective layer containing, for example, a hardenable compound, it may be considered to increase the content of the hardenable compound or the thickness of the protective layer, but even in such cases, the elimination of the aforesaid defects in the continuous images is insufficient, and additional problems, such as reduction in resolving power and changes in quality, etc., occur by the reaction of the hardenable compound and compound(s) in the light-sensitive layer. Also, in the case of forming the surface protective layer containing fine particles alone, the increase of the content of the fine particles or the thickness of the protective layer results in the reduction of resolving power or the reduction of the transparency of the recording material.
As described above, in a transparent light-sensitive recording material having a surface protective layer containing a hardenable compound or fine particles individually, it is difficult to eliminate fine uneven densities occurring on the continuous images formed thereon after running of the recording material or after storage of the recording material in a rolled state for a long period of time. Thus, in the case of forming continuous tone images on a long transparent light-sensitive recording material in a system of running the recording material, it is also required to overcome the above-described problems.